A polarizing plate used in the liquid crystal display or the like is a laminated body comprising a polarizer and a protective film.
As the polarizer constituting the polarizing plate, used is usually a film obtained by having iodine or diachronic dye adsorbed to polyvinyl alcohol film made by a casting method and drawing the adsorbed film in a boric-acid solution.
On the other hand, as the protective film constituting the polarizing plate, triacetyl cellulose film is widely used. However, the triacetyl cellulose film is poor in moisture proof and gas barrier performance, which does not allow the polarizing plate to be sufficient in durability, heat resistance, mechanical strength and the like.
In order to improve durability and heat resistance of the polarizing film, use of a protective film other than triacetyl cellulose film is proposed. For example, in Patent Document 1, use of a laminated film comprising a norbornene resin layer and a resin layer with a small haze value as a protective film is proposed. And this protective film with the norbornene resin layer faced with a polarizer is affixed on the polarizer comprising polyvinyl alcohol to obtain a polarizing plate.
Patent Document 2 proposes a protective film with a small photoelastic coefficient in which a resin layer having hygroscopicity smaller than that of triacetyl cellulose and a positive photoelastic coefficient and a resin layer having hygroscopicity smaller than that of triacetyl cellulose and a negative photoelastic coefficient are laminated. And disclosed is a polarizing plate obtained by affixing this protective film onto a polarizer comprising polyvinyl alcohol.    [Patent Document 1] Japanese Patent Laid-Open No. 2005-115085    [Patent Document 2] Japanese Patent Laid-Open No. 2000-206303